1. Field of the Invention
The invention relates to a device for detecting the position of rotating objects, the device having an optical signal transmitter and an optical sensor.
Detecting the position of rotating objects, in particular, rotating shafts, is frequently performed in machine construction or engineering with the aid of reticles which rotate with the object and are evaluated by a sensor. It is thereby possible to determine the speed, position and, if appropriate, the direction of rotation of the rotating object.
Such devices, however, are not suitable for detecting position with high precision, such as is required, for example, in electronic reproduction technology when exposing recording material by an electronic recording unit, also known as a recorder or an image setter, in order to achieve a good recording quality.
A light beam modulated by an image signal is guided in a recorder over a recording material to be exposed in a punctiform and line-wise manner by a rotating light-beam deflecting device. In this process, the recording material is fixed on a holder which moves relative to the light-beam deflecting device. In order to attain a good recording quality, it is necessary to generate a reference pulse, by an exact position detection, by which the deflecting movement of the light beam and the transport of the recording material are synchronized.
A device for generating such a reference pulse has already been disclosed heretofore in the German Published Non-prosecuted Patent Application (DE-OS) 195 16 154. This known device has a fixed or stationary light source which generates a light beam directed onto a rotating object. The light beam is reflected by a mirror disposed on the rotating object onto a stationary optical sensor which generates an electric reference pulse at a defined angular position of the rotating object.
This heretofore known device, however, is also not adequately suitable for satisfying increased demands for accurate position detection.